This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Because oxidative damage results in aging, cells have a variety of mechanisms to protect against oxidative damage and to repair themselves once damage is done. Proper storage and sequestration of micronutrients, such as metals, is essential to protecting cells from damage when they come under stressful conditions. Since the transport, storage and use of micronutrients is more complex in multicellular organisms, the tactics used by unicellular organisms are being investigated in this study with hopes of extrapolating the findings to larger more complex organisms. The green algae Chlamydomonas reinhardtii adapts well to its environment and can grow under various conditions of salinity, moisture, temperature, light intensity and micronutrient availability. Part of its versatility comes from that fact that it is able to grow heterotrophically in the dark with acetate as its reduced carbon source or to grow phototrophically with sunlight and carbon dioxide. This demonstrates the fact that C. reinhardtii can use either the chloroplasts or mitochondria in response to metabolic demands and raises the question of how the micronutrients are allocated in the cell with respect to metabolic demand. The algae have several protective and preventative mechanisms for avoiding oxidative damage when faced with adverse conditions. What is not understood is how the essential metals and micronutrients are transported, sequestered, stored or re-allocated when cells are confronted with these stressful conditions. This project is designed to probe the assimilation of the micronutrient molybdenum when C. reinhardtii is under conditions of oxidative stress.